JB is a 62-year-old female who visited her primary care physician. Her symptoms included muscle cramps, weakness, and dizziness as well as gastrointestinal distress (nausea, vomiting, and diarrhea). Previous medical history includes diabetes mellitus and progressively impaired renal function. Her physician withdrew blood for a series of lab tests. The results indicated that the patient had a serum potassium level of 6.2 mmol/L. Other serum electrolytes were within the normal ranges.